text: The limiting condition is obtained by noting that pure outflow is impossible when , which implies  from the governing equation. Thus beyond this critical conditions, no solution exists. The critical angle  is given by
  where
  where  is the complete elliptic integral of the first kind. For large values of , the critical angle becomes .
  The corresponding critical Reynolds number or volume flux is given by
  where  is the complete elliptic integral of the second kind. For large values of , the critical Reynolds number or volume flux becomes .